A widescreen optical sense-control system, such as an optical touch-panel system, has a wide application such as an electronic whiteboard (E-Board). FIG. 1 is a schematic diagram illustrating a user using a conventional optical sense-control system. As depicted in FIG. 1, the conventional optical sense-control system 10 mainly includes a touch-control panel 12. While the user 14 inputs information on the touch-control panel 12 via a light pen 16, the inputted information is displayed on the touch-control panel 12.
To make the user 14 can use the optical sense-control system 10 more conveniently, the light pen 16 is designed to be capable of emitting lights with different colors and the optical sense-control system 10 can perform a specific response action based on the color of the light received by the optical sense-control system 10. For example, information of a specific color or of that a specific command has been executed may be displayed on the touch-control panel 12 while a corresponding color of light is detected on the touch-control panel 12.
Different wavelengths have different transmission ratios (or, intensities) to a same optical filter; this can be used for distinguishing the colors of light. FIG. 2 is a schematic chart illustrating the filtering characteristics of the wavelength, transmission ratio and intensity of a blue-light filter, a green-light filter, and a red-light filter which are adopted in the conventional optical sense-control system 10. As depicted in FIG. 2, the blue light B, the green light G, and the red light R are defined with different wavelengths λ and frequencies f, based on the transmission ratios T or intensity I thereof relative to the blue-light filter, the green-light filter, and the red-light filter of the optical sense-control system 10; where the wavelength λ and the frequency f are reciprocal to each other. As depicted in FIG. 2, in the conventional optical sense-control system 10, the blue light B is defined to include the lights with wavelengths within a waveband Bλ; the green light G is defined to include the lights with wavelengths within a waveband Gλ, the red light R is defined to include the lights with wavelengths within a waveband Rλ. Because the blue light B, the green light G, and the red light R are defined in three different specific wavebands in the optical sense-control system 10, a specific response action is accordingly performed while a corresponding light with a specific wavelength, which is emitted from the light pen 16, is detected by the touch-control panel 12. For example, please refer to both FIG. 1 and FIG. 2, a control signal corresponding to the blue light B is created by the optical sense-control system 10 while a light L1 with a wavelength located within the waveband Bλ, is detected on the touch-control panel 12.
However, as depicted in FIG. 2, there are overlaps between the definitions of the blue light B, the green light G, and the red light R in the conventional optical sense-control system 10. If a specific light with a wavelength which are located in the overlap waveband of any two of the wavebands Bλ, Gλ, Rλ, the conventional optical sense-control system 10 may result in an error detection of the specific light and accordingly perform an error response action. For example, please refer to FIG. 1 and FIG. 2 again, if a light L2, having a wavelength located in both the waveband Bλ and the waveband Gλ, is emitted to the touch-control panel 12 from the light pen 16, the optical sense-control system 10 may create a control signal corresponding to both the blue light B and the green light G due to both the blue-light filter (not shown) and the green-light filter detect the light L2, even though the light L2 had a much higher transmission ratio to the blue-light filter than that to the green-light filter.